Praseodymium

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Praseodymium

For other meanings of the abbreviation Pr, see PR.

Praseodymium is a chemical element in the periodic table that has the symbol Pr and atomic number 59.

Notable characteristics

Praseodymium is a soft silvery metallic element, and belongs to the lanthanide group. It is somewhat more resistant to corrosion in air than europium, lanthanum, cerium, or neodymium, but it does develop a green oxide coating that spalls off when exposed to air, exposing more metal to oxidation. For this reason, praseodymium should be stored under a light mineral oil or sealed in glass.

Applications

Uses of praseodymium:

As an alloying agent with magnesium to create high-strength metals that are used in aircraft engines.
Praseodymium forms the core of carbon arc lights which are used in the motion picture industry for studio lighting and projector lights.
Praseodymium compounds are used to give glasses and enamels a yellow color.
Praseodymium is a component of didymium glass, which is used to make certain types of welder's and glass blower's goggles.
Dr. Matthew Sellars of the Laser Physics Centre at the Australian National University in Canberra, Australia slowed down a light pulse to a few hundred meters per second using Praseodymium mixed with silicate crystal.

History

The name Praseodymium comes from the Greek prasios, meaning green, and didymos, or twin.

In 1841, Mosander extracted the rare earth didymium from lanthana. In 1874, Per Teodor Cleve concluded that didymium was in fact two elements, and in 1879, Lecoq de Boisbaudran isolated a new earth, Samarium, from didymium obtained from the mineral samarskite. In 1885, the Austrian chemist baron Carl Auer von Welsbach separated didymium into two elements, Praseodymium and Neodymium, which gave salts of different colors.

Occurrence

Praseodymium is found in the rare earth minerals monazite and bastnasite, and can be recovered from bastnasite or monazite by an ion exchange process. Praseodymium also makes up about 5% of Misch metal.

Compounds

Praseodymium compounds include:

See also Praseodymium compounds.

Isotopes

Naturally occurring praseodymium is composed of one stable isotope, ¹⁴¹Pr. 38 radioisotopes have been characterized with the most stable being ¹⁴³Pr with a half-life of 13.57 days and ¹⁴²Pr with a half-life of 19.12 hours. All of the remaining radioactive isotopes have half-lifes that are less than 5.985 hours and the majority of these have half lifes that are less than 33 seconds. This element also has 6 meta states with the most stable being ^138mPr (t_½ 2.12 hours), ^142mPr (t_½ 14.6 minutes) and ^134mPr (t_½ 11 minutes).

The isotopes of praseodymium range in atomic weight from 120.955 u (¹²¹Pr) to 158.955 u (¹⁵⁹Pr). The primary decay mode before the stable isotope, ¹⁴¹Pr, is electron capture and the primary mode after is beta minus decay. The primary decay products before ¹⁴¹Pr are element 58 (Cerium) isotopes and the primary products after are element 60 (Neodymium) isotopes.

Precautions

Like all rare earths, praseodymium is of low to moderate toxicity. Praseodymium has no known biological role.

References

Los Alamos National Laboratory – Praseodymium

External links

Chemical elements | Lanthanides

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